Measuring device for contactless distance measurement

ABSTRACT

A measuring device for contactless distance measurement is disclosed, which has an optical transmission path ( 12 ), with an optical transmitter ( 22 ), and an optical receiver ( 13 ), with a receiving optical element ( 29 ) and an optical receiver ( 30 ), as well as an equipment module ( 11 ) that receives these components of the transmission and reception paths ( 12, 13 ). To maintain high measurement precision over the entire temperature range, the components of the transmission and reception paths ( 12, 13 ) are placed such that upon a temperature-dictated curvature of the equipment module ( 11 ) in the direction of the optical axes ( 121, 131 ) of the transmission and reception paths ( 12, 13 ), the optical axes ( 121, 131 ) are deflected in the same direction by the same amount. For this purpose, the transmission and reception paths ( 12, 13 ) are preferably convoluted such that the transmitter ( 22 ) and receiver ( 30 ) are both located on the same flat fastening face, fixed in the equipment module ( 11 ), the fastening face preferably being a printed circuit board ( 15 ) for receiving electronic components (FIG.  2 ).

PRIOR ART

[0001] The invention relates to a measuring device for contactlessdistance measurement, in particular a handheld device, as genericallydefined by the preamble to claim 1.

[0002] One such measuring device, designed as a handheld device and alsoknown as a distance measuring device, is known for instance from GermanPatent Disclosure DE 198 04 051 A1 or German Patent DE 196 52 438 C2.The measuring device operates on the principle of transit timemeasurement, in that a light signal or light pulse is transmitted fromthe transmission path to the appropriate object, and this signal orpulse is reflected from the object and received again by the measuringdevice via the reception path, and the transit time of the light signalor pulse, which is the period of time between the instant oftransmission and the instant of reception, is measured. This period oftime is a measure for the distance, which is calculated taking the speedof light into account and is shown on a display. The transit time can bedetermined for instance by correlating the transmission and receptionsignals.

ADVANTAGES OF THE INVENTION

[0003] The measuring device for contactless distance measurementaccording to the invention has the advantage that because of theplacement according to the invention of the components, it is attainedthat over the entire temperature range, the light spot produced on anappropriate object by the optical transmission path is replicated in theoptical reception path and is thus seen. Hence a temperature-causedcurvature of the equipment module that carries the components does notaffect the measurement operation, and via the optical reception path,the maximum possible light intensity of the beam transmitted over theoptical transmission path is always received, so that the measurementsensitivity of the measuring device is also preserved over the entiretemperature range.

[0004] By the provisions recited in the further claims, advantageousrefinement of and improvements to the measuring device disclosed inclaim 1 are possible.

[0005] In a preferred embodiment of the invention, the transmission andreception paths are optically convoluted such that the transmitter andthe receiver are both located in the same flat fastening face, which isfixed in the equipment module. By the convolution of the two opticalpaths, on the one hand the receiving optical element can be shorter, buton the other, without additional optical components, such as opticalwaveguides that markedly reduce the efficiency of the receiving opticalelement, the transmitter and receiver can be placed in the samefastening face. If the equipment module curves in response totemperature, then the fastening face fixed on it also curves, and thelight spot generated by the transmitter on the object being measured,and the field of view of the receiver on the object being measured,migrate in the same way. The light spot and field of view thus remaincongruent even if the temperature changes.

[0006] In an advantageous embodiment of the invention, the equipmentmodule has an optical element mount and a printed circuit board that isfirmly connected to the optical element mount and that forms thefastening face for the optical transmitter and the optical receiver. Theoptical convolution of the transmission and reception paths is done bymeans of a deflecting mirror disposed in the optical element mount.Because the transmitter and receiver, including their electroniccomponents, are accommodated on the same printed circuit board,automatic contacting of the transmitter and receiver and theircomponents is possible in a way that is simple from a productionstandpoint, and at the same time simple shielding from the outsideenvironment is feasible, especially if in an advantageous embodiment ofthe invention the electronic components are disposed on the underside,toward the optical element mount, of the printed circuit board. Then,such shielding can be realized in a simple way by a shielding layer inthe preferably multi-layer printed circuit board, which is connectedelectrically conductively to the optical element mount at at least onepoint.

[0007] In a preferred embodiment of the invention, the printed circuitboard extends as parallel as possible to a plane that extends throughthe optical axes of the transmission and reception paths. As a result,the available installation space in the equipment module is optimallyutilized, and the free back side of the printed circuit board can beused to accommodate operator control elements and displays.

[0008] In an advantageous embodiment of the invention, the deflectingmirror is designed as an optical filter, in order to limit the bandwidthof the light reflected from the appropriate object and received by theoptical receiver.

[0009] In an advantageous embodiment of the invention, the transmissionand reception paths are separated from one another by chambers andchannels embodied in the optical element mount, so that on the one handno light from the transmission beam reaches the receiver, and on theother, by electrical shielding, crosstalk between the signals on thetransmitter and receiver sides is markedly reduced.

[0010] In an advantageous embodiment of the invention, a closable windowis provided in a partition in the optical element mount that separatesthe channel for the transmission path from the channel for the receptionpath. Furthermore, a deflecting element is disposed in the channel forthe transmission path and is pivotable into the transmission path insuch a way that a transmitted light beam striking the deflecting elementis introduced through the window into the reception path. Mostpreferably, the deflecting element, in its position pivoted out of thetransmission path, closes the window in the partition between the twochannels. This mechanism is intended for purposes of a referencemeasurement, so that the measuring device can be calibrated accordingly.

DRAWING

[0011] The invention is described in further detail in the ensuingdescription in terms of an exemplary embodiment shown in the drawing.Shown are:

[0012]FIG. 1, a perspective view from below of an equipment module withthe components of the transmission and reception paths of a distancemeasuring device;

[0013]FIG. 2, a section taken along the line II-II in FIG. 1;

[0014]FIG. 3, a section taken along the line III-III in FIG. 2;

[0015]FIG. 4, a section taken along the line IV-IV in FIG. 2.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0016] The equipment module 11, which can be seen in perspective frombelow in FIG. 1 and in various sectional views in FIGS. 2-4, and whichonce the measuring device has been completely assembled is enclosed by ahousing, carries the components for embodying an optical transmissionpath 12 and an optical reception path 13. The equipment module 11 has anoptical element mount 14 and a printed circuit board 15 that is securedto the optical element mount 14 by means of screws 16 (FIGS. 3 and 4).The printed circuit board 15 is disposed on the optical element mount 14as parallel as possible to a plane that extends through the optical axes121 and 131 (FIG. 2) of the transmission path 12 and reception path 13,and in FIG. 2 it coincides with the plane of the paper. The transmissionand reception paths 12, 13 are separated from one another by channelsand chambers 18-21 embodied in the optical element mount 14. In FIG. 3,the transmission channel 18 and the transmission chamber 19, which isoriented perpendicular to the transmission channel 18, can be seen, andin FIG. 4, the reception channel 20 and the reception chamber 21, whichis likewise oriented perpendicular to the reception channel 20, can beseen. In a sectional view of FIG. 2, the disposition of the transmissionchannel 18 and reception channel 20 in the optical element mount 14 canbe seen.

[0017] The components of the optical transmission path 12 include anoptical transmitter 22, which is embodied as a collimator 24 with alaser diode 25 and a collimator lens 26 (FIG. 3); a cover disk 27 ofglass, which closes off the transmission channel 18 at the front; and adeflecting mirror 28, disposed on the other end of the transmissionchannel 18, which is retained adjustably on the optical element mount14. The optical axis 121 of the transmission path 131 can be adjustedvia the deflecting mirror 28.

[0018] The components of the optical reception path 13 include areceiving optical element 29 and a receiver 30, downstream of it, whichis embodied here as a light detector 31 (FIG. 4). The receiving opticalelement 29 comprises a receiver lens, closing off the reception channel20 at the front, with a long focal length, and a deflecting mirror 33,which is placed on the other end of the reception channel 20 and isretained adjustably in the optical element mount 14. Via the deflectingmirror 33, both the focal point and the direction of the ok 131 of thereception path 13 can be varied and adjusted.

[0019] Both the collimator 24 and the light detector 31 are secured tothe printed circuit board 15, specifically on the underside, toward theoptical element mount 14, and are put into contact there with furtherelectronic components, not shown here, of the transmitter 22 andreceiver 30 that are also located on the underside of the printedcircuit board 15. The shielding of the transmitter 22 and receiver 30and electronic components from the outside is effected by a shieldinglayer, not shown here, in the printed circuit board 15, which isembodied as multi-layered and is connected electrically conductively atat least one point to the optical element mount 14. The transmitter 22and receiver 30 are disposed close together with spacing, transverselyto the optical axis 121, 131, and the collimator 24 protrudes into thetransmission chamber 19 and the light detector 31 protrudes into thereception chamber 21, and thus the transmitter 22 and receiver 30 areshielded from one another both optically and electrically. Because ofthis placement of the transmitter 22 and receiver 30, a deformation,resulting from the connection of the printed circuit board 15 and theoptical element mount 14, of the optical element mount 14 upon atemperature response that causes a curvature of the optical elementmount 14 in the direction of the optical axes 121, 131, the optical axes121, 131 of the transmission path 12 and reception path 13 are deflectedby the same amount in the same direction. As a result, once thetransmission path 12 and reception path 13 have been adjusted once andfor all by the deflecting mirrors 28, 33, the measurement spot generatedon an appropriate object by the transmission path 12 is always fullyreplicated on the light detector 31 in the reception path 13, so thatthe curvature of the optical element mount 14 does not affect themeasurement precision of the device.

[0020] As can be seen in FIGS. 2 and 3, a window 35 is provided in apartition 34 that separates the transmission channel 18 from thereception channel 20, and a deflecting element 36 is disposed pivotablyin the transmission channel 18 in such a way that it can be pivoted intothe beam path in the transmission channel 18, or in other words into thetransmission path 12, and out of the beam path in the transmissionchannel 18, that is, out of the transmission path 12, again. In theinward-pivoted position, the deflecting element 36 deflects a beam,arriving from the deflecting mirror 28, through the window 35 into thereception channel 20, where the beam, via a reflector 37 (FIG. 2) andthe deflecting mirror 33, strikes the light detector 31. In theoutward-pivoted position, the deflecting element 36 closes the window35. This pivoting mechanism of the deflecting element 36 serves toperform a reference measurement, for calibrating the measuring device.

1. A measuring device for contactless distance measurement, inparticular a handheld device, having an optical transmission path (12),which has an optical axis (121) and as one component has an opticaltransmitter (22), having an optical reception path (13), which has anoptical axis (131) and as components has a receiving optical element(29) and an optical receiver (30), and having an equipment module (11)that receives the components of the transmission and reception paths(12, 13), characterized by a placement of the components of thetransmission path (12) and reception path (13) such that upon atemperature-caused curvature of the equipment module (11) in thedirection of the optical axes (121, 131) of the transmission andreception paths (12, 13), the optical axes (121, 131) are deflected bythe same amount in the same direction.
 2. The measuring device of claim1, characterized in that the transmission and reception paths areoptically convoluted such that the transmitter (22) and the receiver(30) are both located in the same flat fastening face, which is fixed inthe equipment module (11).
 3. The measuring device of claim 2,characterized in that the equipment module (11) has an optical elementmount (14) and a printed circuit board (15), which is firmly connectedto the optical element mount (14) and forms the fastening face for theoptical transmitter (22) and the optical receiver (30), and that for theoptical convolution of the transmission and reception paths (12, 13),one deflecting mirror (28, 33) per path is disposed in the opticalelement mount (14).
 4. The measuring device of claim 3, characterized inthat the printed circuit board (15) is oriented as parallel as possibleto a plane extending through the optical axes (121, 131) of thetransmission and reception paths (12, 13).
 5. The measuring device ofclaim 3, characterized in that the optical transmitter (22) and theoptical receiver (30) are disposed on the inside, oriented toward theoptical element mount (14), of the printed circuit board (15),transversely to the optical axes (121, 131) of the transmission andreception paths (12, 13), and spaced apart from one another.
 6. Themeasuring device of claim 3, characterized in that the deflectingmirrors (28, 33) are embodied as optical filters.
 7. The measuringdevice of claim 3, characterized in that the optical transmitter (22)and the optical receiver (30) have electronic components, which aredisposed on the underside, oriented toward the optical element mount(14) of the printed circuit board (15), and that the printed circuitboard (15) has at least one shielding layer for electronic shieldingfrom the outside.
 8. The measuring device of claim 7, characterized inthat with its shielding layer, the printed circuit board (15) iselectrically conductively connected to the optical element mount (14) atat least one point.
 9. The measuring device of claim 3, characterized inthat the transmission and reception paths (12, 13) are separated fromone another by channels (18, 20) and chambers (19, 21) embodied in theoptical element mount (14).
 10. The measuring device of claim 9,characterized in that the axes of the channels (18, 20) are oriented asparallel as possible to the optical axes (121, 131) of the transmissionand reception paths (12, 13).
 11. The measuring device of claim 10,characterized in that the channels (18, 20) are closed off at the ends,each by a respective optically transparent element (27, 32).
 12. Themeasuring device of claim 9, characterized in that a closable window(35) is provided in a partition (34) of the optical element mount (14),which partition separates the channel (18) for the transmission path(12) from the channel (20) for the reception path (13), and a deflectingelement (36) is disposed in the channel (18) for the transmission path(12), which deflecting element can be pivoted into the transmission path(12) in such a way that a transmitted light beam, striking thedeflecting element (36), is introduced through the window (35) into thereception path (13).
 13. The measuring device of claim 12, characterizedin that the deflecting element (36), in its position pivoted out of thetransmission path (12), closes the window (35) in the partition (34).14. The measuring device of claim 1, characterized in that the opticaltransmitter (22) is a collimator (24), with a laser diode (25) and acollimator lens (26).
 15. The measuring device of claim 1, characterizedin that the optical receiver (30) has a light detector (31).